The invention is based on a controlled rectifier bridge with surge protection for a generator, in particular for a rotary current generator used in a vehicle, as generically defined by the preamble to the main claim.
1. Prior Art
Electrical energy for an on-board vehicle electrical system is typically done with a rotary current generator driven by the internal combustion engine of the vehicle, and the output voltage of the rotary current generator is regulated by a voltage regulator. With the aid of a rectifier bridge, the output voltage of the generator is converted into a direct voltage. Typically six Zener diodes, which are located between the positive and negative terminals of the generator, are used as the rectifier bridge.
However, it is also known instead of Zener diodes to use triggerable rectifier elements that are triggered by control means. The use of a controlled rectifier bridge is described for instance in U.S. Pat. No. 4,825,139. The use of MOS field effect transistors in the rectifier bridge is also proposed there. With the aid of a controlled rectifier bridge of this kind, a generator regulation can be performed that even at low rpm makes a generator output voltage possible that is suitable for supplying the vehicle electrical system.
2. Advantages of the Invention
The controlled rectifier bridge of the invention with protection circuit has the advantage over the prior art that the voltage peaks that occur upon a load dump are reduced. Reducing these voltage peaks is necessary if a self-controlled rectifier bridge with MOS field effect transistors is used.
These advantages are attained by using a controlled rectifier bridge with protection circuit as defined by the combination of characteristics of claim 1. With this controlled rectifier bridge with protection circuit, the voltage surges that occur upon a load dump as a result of the magnetic energy stored in the exciter winding of the generator are rapidly reduced, because the stored energy is fed back into the battery.
Further advantages of the invention are attained by the provisions recited in the dependent claims. It is especially advantageous that as a result of the feedback of the exciter current, a rapid drop in the load-dump voltage caused by the load dump is attained; the short-circuit current caused by this load-dump voltage, which in the event of a short circuit has to be controlled by the MOS field effect transistors, can be kept especially low.